1. Field of the Invention
This invention relates to motor driven winding-up mechanisms for cameras and more particularly controls rotation of the motor.
2. Description of the Prior Art
In the conventional motor driven winding-up mechanism for a camera, when the film has been wound-up one frame, the stopping member latches the driving torque transmission system for the sprocket and the takeup spool so that their rotation is stopped. And, at the same time the current supplied to the motor is stopped. With this, however, because the inertia of the motor and transmission system is retained in the form of stress at the various members of the transmission system and the stopping member, to initiate the next cycle of the winding operation, since the heavy overload lies on the stopping member, the required magnitude of force for releasing the transmission system from the locking connection is very large. This problem becomes serious when a series of continuous shots are to be made. If the winding-up stopping member is not smoothly moved away from the transmission system, the time interval between the successive two shots is randomly varied to a great extent.
To improve this, a previous proposal is shown in FIG. 5 where an automatic winding-up unit 102 for a camera 101 includes an electric motor 103, and gears 104 to 108 constitute a transmission system, which terminates at a female coupler 109 engaging a male coupler 110 within the camera housing. The gears 106 and 107 are connected to each other by a shaft 111 on which are mounted a fly wheel 112 and a coil spring 113. Based on this proposal, at the termination of the winding-up operation, the inertia of the transmission system allows the fly wheel 112 to further rotate while charging the spring 113. After the torque of the fly wheel 112 has been balanced with the bias force of the spring 113, it rotates in the reverse direction, whereby the overload on the coupler 110 is removed. By this method, however, it takes the fly wheel 112 a long time to rest so that when a series of continuous shots is taken, it cannot fully function. Moreover, an alternative problem which is produced is that the production cost is increased by the increased number of parts, and the size of the drive or wind-up unit 102 is increased.
Another proposal in U.S. Pat. No. 4,182,562 is that after termination of each cycle of winding, the motor is over-driven by using a delay means so that the driving torque transmission and the winding-up stopping member are given an excessive load. Then, the reaction of their strain produces a discouraging effect. However, this method requires that the transmission system and the stopping member be made of elastic material. Another disadvantage is that with the battery to dropped voltage, the large overload is unsolved, or rather intensified.
Also, Japanese Laid-Open Patent Application No. SHO 53-39123 purposes the use of an electromagnetic clutch to stop rotation of the motor just when the winding-up operation terminates resulting in no overload is given to the transmission system and the stopping member. This method, however, has the disadvantage that the usable electromagnetic clutch is very expensive and large.
An object of the present invention is to provide a motor driven winding-up mechanism for a camera in which the stress resulting from the inertia of the motor when the winding is completed is removed by very simple means and low cost. Thereby it is possible to make a series of continuous shots smoothly.
Other objects of the invention will become apparent from the following detailed description thereof.